Question

Suppose a 480. mL flask is filled with 0.720 mol of N2 and 1.32 mol of NO. This reaction becomes possible: N2 (g) + O2 (g) ⇌ 2 NO(g)

The equilibrium constant Kc is 7.62 at the reaction temperature.

• Calculate the equilibrium molarity of O2 .

• (Round final answer to two decimal places.)

Answer 1

The given equilibrium is

Volume of the flask = 480. mL = 0.480 L

Hence, we can calculate the initial concentrations in molarity unit from the given number of moles of substance present.

Note that only one of the reactant is present at the beginning. Hence, the reaction cannot proceed in forward direction.

Hence, some of the product NO will convert to reactants to reach equilibrium.

Now, we can create an ICE table to calculate the equilibrium concentrations.

Initial, M	1.50	0	2.75
Change, M	+x	+x	-2x
Equilibrium, M	1.50+x	x	2.75-2x

Note that when 2x moles of NO are consumed, we get x moles each of N₂ and O₂ as predicted by the balanced equation.

Now, we can write the expression of equilibrium constant K_c using the ICE table as follows:

Hence, using the ICE table the equilibrium concentrations are

Hence, the equilibrium molarity of O₂ is 0.32 M. (Rounded to two decimal places.)